Substances such as bilirubin that bind tightly to plasma protein cannot be removed by dialysis. We have attempted to remove such substances by employing affinity chromatography on protein - agarose beads. Human albumin is conjugated to agarose: the resulting beads are placed in a column and plasma or whole blood, are passed over the column. Bilirubin or other substances are assayed before and after passage. The bound material is eluted and assayed.